This page presents an overview of the pre-mining resources for the non-alluvial deposits of Tasmania. The deposits are grouped according to their age and style of mineralisation.
The Cambrian age Mount Read Volcanic (MRV) rocks are the economically most important rocks in Tasmania. These are included below but are also discussed separately (click here), along with 2012 estimates of in-ground value based on pre-mining resource and current reserves.
From oldest to youngest….
Precambrian deposits in the Arthur Lineament
The term Arthur Lineament strictly refers to a narrow (110 km long by up to 10 km wide) tectonic feature which transects northwest Tasmania from the west coast to the north coast. The Arthur Lineament hosts economically important iron ore and magnesite deposits (below).
The Savage River magnetite mine consists of sub-vertical, concordant lenses of massive magnetite ore with varying amounts of pyrite and trace chalcopyrite in a sequence of tholeiitic amphibolite of extrusive and intrusive origin, carbonates and serpentinite. Magnesite deposits of high purity and substantial size are known at Arthur River, Lyons River, and Main Creek.
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Savage River 371 Mt @ 31.9% Fe
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Arthur River 29 Mt @ 42.8% Mg
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Main Creek 42.8 Mt @ 42.4% Mg
Cambrian gabbro-hosted deposits
Ultamafic complexes across much of cenral northern and western tasmania are the product of ancient oceanic crust that has been faulted and thrust. This crust now forms a disaggregated and folded sheet. Like ultramafic complexes elsewhere in the world, those in Tasmania host metals. In places these mineralised rocks have been intruded by granites which appear to have upgraded and/or introduced mineralisation.
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Nickel Reward (Cuni field) 0.03 Mt @ 3% Ni
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North Cuni–Genets Winze 0.95 Mt @ 0.76% Ni, 0.94% Cu
Cambrian deposits in the Mount Read Volcanics
The most important metallogenic event in Tasmania coincided with the deposition of the Mount Read Volcanics (MRV). Mineralisation was concentrated in a short time interval in the late Middle Cambrian. Major alteration zones are dominantly of quartz-sericite mineralogy.
The Henty Fault constitutes a fundamental tectonic divide within the MRV. To the northwest, polymetallic Zn-Pb-Au-Ag-Cu massive sulfide deposits dominate (Hellyer, Que River, Rosebery, Hercules) together with disseminated deposits with lower base metal, but relatively high Au and Ag tenor (Mount Charter, South Hercules). Southeast of the Henty Fault copper-gold and gold deposits dominate, exemplified by the Mount Lyell field and the Henty gold deposit. The most economically important deposits in the Mount Lyell field are disseminated chalcopyrite-pyrite orebodies in alteration assemblages dominated by quartz-sericite or quartz-chlorite-sericite.
Historically, most mineralisation within the MRV has been associated with sea floor volcanism (VHMS-style). This model has driven much of the exploration, with programs strongly biased toward locating strata-parallel mineralisation. More recent discovery of the fault-related henty gold deposit and a shift toward Mt Lyell being of a hybrid VHMS-porphyry style has opened new opportunities to reassess earlier results.
Paragon Resources Elliott Bay tenement in the southern MRV is another example of gold mineralisation that was originally unexplained using a VHMS model but has more recently been attributed to shear-zones. Shear-zone style of mineralisation is common to the WA goldfields where it is similarly associated with VHMS depsoits.
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Hellyer 16.5 Mt @ 13.9% Zn, 7.2% Pb, 0.38% Cu, 169 g/t Ag, 2.55 g/t Au
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Que River 3.3 Mt @ 13.3% Zn, 7.4% Pb, 0.7% Cu, 195 g/t Ag, 3.3 g/t Au
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Mount Charter 6.1 Mt @ 0.5% Zn, 25.5 g/t Ag, 1.22 g/t Au, 9.7% Ba
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Rosebery 34.03 Mt @ 13.8% Zn, 4.1% Pb, 0.57% Cu, 143 g/t Ag, 2.2 g/t Au
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Hercules 3.33 Mt @ 17.3% Zn, 5.5% Pb, 0.4% Cu, 171 g/t Ag, 2.8 g/t Au
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South Hercules 0.56 Mt @ 3.7% Zn, 1.9% Pb, 0.1% Cu, 157 g/t Ag, 3.0 g/t Au
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Henty–Mt Julia 2.83 Mt @ 12.5 g/t Au
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Tasman & Crown Lyell 0.138 Mt @ 10.0% Zn, 8.9% Pb, 0.54% Cu, 212 g/t Ag, 0.35 g/t Au
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Mount Lyell 311 Mt @ 0.97% Cu, 0.31 g/t Au
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Garfield 12 Mt @ 0.3% Cu
Ordovician carbonate-hosted deposits
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Oceana 2.6 Mt @ 7.7% Pb, 2.5% Zn, 55 g/t Ag
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Grieves Siding ~0.7 Mt @ 8% Zn (primary); 0.15 Mt @ 5% Zn (secondary)
Devonian orogenic gold deposits
Deformation-related , vein-style gold depsoits are common to NE Tasmania where they are hosted mainly by the Mathinna Supergroup turbidite rocks. These deposits are similar to those of Bendigo and Ballarat in Victoria, with host rocks in NE Tasmania similarly correlated with those in Victoria (most likely the Melbourne Zone). The largest Devonian age vein style depsoit is the Tasmania Reef at Beaconsfield. This is Australia’s largest single gold reef. For the most part, however, these Devonian vein-style depsoits tend to be small size, and varying (nuggety) grade.
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Beaconsfield 3.25 Mt @ 19.0 g/t Au
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New Golden Gate 0.51 Mt @ 15.6 g/t Au
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Pinafore Reef (Lefroy) 0.974 Mt @ 10.1 g/t Au
Devonian granite-related tin deposits
Grantie intrusion during the Devonian was widespread across Tasmania. Styles of mineralisation vary and reflect the variable and complex pre-intrusion geology.
Sulfide skarns
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Renison Bell 24.54 Mt @ 1.41% Sn
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Mount Bischoff 10.54 Mt @ 1.1% Sn
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Cleveland 12.4 Mt @ 0.61% Sn, 0.25% Cu
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Foley zone 3.8 Mt @ 0.28% WO3, 0.02% MoS2, 0.05% Sn
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Razorback 0.34 Mt @ 0.9% Sn
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Queen Hill 3.6 Mt @ 1.2% Sn
Silicate skarns
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St Dizier ~2.6 Mt @ 0.5% Sn, 0.05% WO3
Vein deposits
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Aberfoyle 2.1 Mt @ 0.91% Sn, 0.28% WO3
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Pieman vein (East Renison) 0.43 Mt @ 1.0% Sn
Greisen deposits
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Anchor 2.39 Mt @ 0.28% Sn
Other Devonian granite-related deposits
Skarns
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King Island field 23.8 Mt @ 0.66% WO3
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Kara 5.2 Mt @ >30% Fe, by-product WO3
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Avebury 10.04 Mt @ 1.14% Ni
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Moina 18 Mt @ 26% CaF, 0.1% Sn, 0.1% WO3
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Hugo (Moina area) 0.25 Mt @ 5.5% Zn, 1 g/t Au, 0.1% Bi
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Stormont (Moina area) 0.135 Mt @ 3.44 g/t Au, 0.21% Bi
Vein deposits
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Storeys Creek 1.1 Mt @ 1.09% WO3, 0.18% Sn
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Magnet 0.63 Mt @ 7.3% Zn, 7.3% Pb, 427 g/t Ag
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Salmons Vein (East Renison) 0.83 Mt @ 3.2% Pb, 2.2% Zn, 104 g/t Ag, 0.19% Sn, 0.61% Cu
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New North Mount Farrell and North Mount Farrell 0.908 Mt @ 12.5% Pb, 2.5% Zn, 408 g/t Ag
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Lakeside 0.75 Mt @ 0.2% Sn, 0.2% Cu, 4.0% As, 2.1 g/t Au, 20 g/t Ag
The figures are estimates only based on historical information and are not JORC-compliant.
(Source: MRT 2007)